Suppression of cellular invasion by glybenclamide through inhibited secretion of platelet-derived growth factor in ovarian clear cell carcinoma ES-2 cells

Methionine aminopeptidase‑2 is a pivotal regulator of vasculogenic mimicry

Vasculogenic mimicry (VM) is the formation of a blood supply system that confers aggressive and metastatic properties to tumors and correlates with a poor prognosis in cancer patients. Thus, the inhibition of VM is considered an effective approach for cancer treatment, although such a mechanism remains poorly described. In the present study, we examined methionine aminopeptidase-2 (MetAP2), a key factor of angiogenesis, and demonstrated that it is pivotal for VM, using pharmacological and genetic approaches. Fumagillin and TNP-470, angiogenesis inhibitors that target MetAP2, significantly suppressed VM in various human cancer cell lines. We established MetAP2-knockout (KO) human fibrosarcoma HT1080 cells using the CRISPR/Cas9 system and found that VM was attenuated in these cells. Furthermore, re-expression of wild-type MetAP2 restored VM in the MetAP2-KO HT1080 cells, but the substitution of D251, a conserved amino acid in MetAP2, failed to rescue the VM. Collectively, our results demonstrate that MetAP2 is critical for VM in human cancer cells and suggest fumagillin and TNP-470 as potent VM-suppressing agents.

Cancer and diabetes: the interlinking metabolic pathways and repurposing actions of antidiabetic drugs

Cancers are regarded as one of the main causes of death and result in high health burden worldwide. The management of cancer include chemotherapy, surgery and radiotherapy. The chemotherapy, which involves the use of chemical agents with cytotoxic actions is utilised as a single treatment or combined treatment. However, these managements of cancer such as chemotherapy poses some setbacks such as cytotoxicity on normal cells and the problem of anticancer drug resistance. Therefore, the use of other therapeutic agents such as antidiabetic drugs is one of the alternative interventions used in addressing some of the limitations in the use of anticancer agents. Antidiabetic drugs such as sulfonylureas, biguanides and thiazolidinediones showed beneficial and repurposing actions in the management of cancer, thus, the activities of these drugs against cancer is attributed to some of the metabolic links between the two disorders and these includes hyperglycaemia, hyperinsulinemia, inflammation, and oxidative stress as well as obesity. Furthermore, some studies showed that the use of antidiabetic drugs could serve as risk factors for the development of cancerous cells particularly pancreatic cancer. However, the beneficial role of these chemical agents overweighs their detrimental actions in cancer management. Hence, the present review indicates the metabolic links between cancer and diabetes and the mechanistic actions of antidiabetic drugs in the management of cancers.

Regulation of N-glycosylation and secretion of Isthmin-1 by its C-mannosylation

BACKGROUND

C-mannosylation is a type of protein glycosylation. Human Isthmin-1 (ISM1) is a 52-kDa secreted protein with a thrombospondin type 1 repeat (TSR) domain, containing two consensus C-mannosylation sequences at Trp²²³ and Trp²²⁶. In this study, we sought to examine the role of C-mannosylation in the secretion of ISM1.

METHODS

We established and cultured an ISM1-overexpressing HT1080 cell line and purified recombinant ISM1 for analysis from the conditioned medium by LC-MS/MS. Subcellular localization of ISM1 was observed by confocal fluorescence microscopy.

RESULTS

We found that ISM1 is C-mannosylated at Trp²²³ and Trp²²⁶ in the TSR domain. To determine the functions of the C-mannosylation of ISM1, we established a C-mannosylation-defective mutant ISM1-overexpressing HT1080 cell line and measured its secretion of ISM1. The secretion of ISM1 decreased significantly in this mutant ISM1-overexpressing line compared with wild-type cells. Furthermore, ISM1 was N-glycosylated only in these C-mannosylation-defective cells.

CONCLUSIONS

ISM1 is C-mannosylated in its TSR domain, and the status of the C-mannosylation of ISM1 affects its N-glycosylation.

GENERAL SIGNIFICANCE

The C-mannosylation of ISM1 regulates its N-glycosylation status.

Requirement for C-mannosylation to be secreted and activated a disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS4)

BACKGROUND

C-mannosylation is a unique type of glycosylation. A disintegrin and metalloproteinase with thrombospondin motifs 4 (ADAMTS4) is a multidomain extracellular metalloproteinase that contains several potential C-mannosylation sites. Although some ADAMTS family proteins have been reported to be C-mannosylated proteins, whether C-mannosylation affects the activation and protease activity of these proteins is unclear.

METHODS

We established wild-type and mutant ADAMTS4-overexpressing HT1080 cell lines. Recombinant ADAMTS4 was purified from the conditioned medium of the wild-type ADAMTS4-overexpressing cells, and the C-mannosylation sites of ADAMTS4 were identified by LC-MS/MS. The processing, secretion, and intracellular localization of ADAMTS4 were examined by immunoblot and immunofluorescence analyses. ADAMTS4 enzymatic activity was evaluated by assessing the cleavage of recombinant aggrecan.

RESULTS

We identified that ADAMTS4 is C-mannosylated at Trp⁴⁰⁴ in the metalloprotease domain and at Trp⁵²³, Trp⁵²⁶, and Trp⁵²⁹ in the thrombospondin type 1 repeat (TSR). The replacement of Trp⁴⁰⁴ with Phe affected ADAMTS4 processing, without affecting secretion and intracellular localization. In contrast, the substitution of Trp⁵²³, Trp⁵²⁶, and Trp⁵²⁹ with Phe residues suppressed ADAMTS4 secretion, processing, intracellular trafficking, and enzymatic activity.

CONCLUSIONS

Our results demonstrated that the C-mannosylation of ADAMTS4 plays important roles in protein processing, intracellular trafficking, secretion, and enzymatic activity.

GENERAL SIGNIFICANCE

Because C-mannosylation appears to regulate many ADAMTS4 functions, C-mannosylation may also affect other members of the ADAMTS superfamily.

Cell-dependent regulation of vasculogenic mimicry by carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1)

Vasculogenic mimicry (VM) promotes tumor migration, metastasis, and invasion in various types of cancer, but the relationship between VM and these phenotypes remains undefined. In this study, we examined carcinoembryonic antigen cell adhesion molecule 1 (CEACAM1) as a novel target of VM. We found that ectopic expression of CEACAM1 in HT1080 human fibrosarcoma cells suppressed the formation of a VM-like network. Further, cell migration and proliferation were abated by the introduction of CEACAM1 into HT1080 cells. Conversely, knockout (KO) of the CEACAM1 gene in SK-MEL-28 melanoma cells, which normally express high levels of CEACAM1, inhibited formation of a VM-like network, which was covered on reintroduction of CEACAM1. These results suggest that CEACAM1 differentially regulates formation of the VM-like network between cancer cell types and implicate CEACAM1 as a novel therapeutic target in malignant cancer.

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CEACAM1 is not expressed in HT1080 cells, and overexpression of CEACAM1 in HT1080 cells suppresses vasculogenic mimicry.

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CEACAM1 is highly expressed in SK-MEL-28 cells, and deletion of CEACAM1 in SK-MEL-28 cells abolishes vasculogenic mimicry.

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CEACAM1 regulates vasculogenic mimicry in a cell-dependent manner.

The Multifaceted Roles of Pyroptotic Cell Death Pathways in Cancer

Cancer is a category of diseases involving abnormal cell growth with the potential to invade other parts of the body. Chemotherapy is the most widely used first-line treatment for multiple forms of cancer. Chemotherapeutic agents act via targeting the cellular apoptotic pathway. However, cancer cells usually acquire chemoresistance, leading to poor outcomes in cancer patients. For that reason, it is imperative to discover other cell death pathways for improved cancer intervention. Pyroptosis is a new form of programmed cell death that commonly occurs upon pathogen invasion. Pyroptosis is marked by cell swelling and plasma membrane rupture, which results in the release of cytosolic contents into the extracellular space. Currently, pyroptosis is proposed to be an alternative mode of cell death in cancer treatment. Accumulating evidence shows that the key components of pyroptotic cell death pathways, including inflammasomes, gasdermins and pro-inflammatory cytokines, are involved in the initiation and progression of cancer. Interfering with pyroptotic cell death pathways may represent a promising therapeutic option for cancer management. In this review, we describe the current knowledge regarding the biological significance of pyroptotic cell death pathways in cancer pathogenesis and also discuss their potential therapeutic utility.

Sulfonylurea derivatives and cancer, friend or foe?

Type 2 diabetes mellitus (T2DM) is associated with a higher risk of cancer and cancer-related mortality. Increased blood glucose and insulin levels in T2DM patients may be, at least in part, responsible for this effect. Indeed, lowering glucose and/or insulin levels pharmacologically appears to reduce cancer risk and progression, as has been demonstrated for the biguanide metformin in observational studies. Studies investigating the influence of sulfonylurea derivatives (SUs) on cancer risk have provided conflicting results, partly due to comparisons with metformin. Furthermore, little attention has been paid to within-class differences in systemic and off-target effects of the SUs. The aim of this systematic review is to discuss the available preclinical and clinical evidence on how the different SUs influence cancer development and risk. Databases including PubMed, Cochrane, Database of Abstracts on Reviews and Effectiveness, and trial registries were systematically searched for available clinical and preclinical evidence on within-class differences of SUs and cancer risk. The overall preclinical and clinical evidence suggest that the influence of SUs on cancer risk in T2DM patients differs between the various SUs. Potential mechanisms include differing affinities for the sulfonylurea receptors and thus differential systemic insulin exposure and off-target anti-cancer effects mediated for example through potassium transporters and drug export pumps. Preclinical evidence supports potential anti-cancer effects of SUs, which are of interest for further studies and potentially repurposing of SUs. At this time, the evidence on differences in cancer risk between SUs is not strong enough to guide clinical decision making.

Identification of topoisomerases as molecular targets of cytosporolide C and its analog

Cytosporolide (Cytos) A-C, isolated from the fungus Cytospora sp., have anti-microbial activity, but their molecular targets in mammalian cells are unknown. We have previously reported the total synthesis of Cytos A by biomimetic hetero-Diels-Alder reaction. In this study, to examine the novel bioactivity of Cytos, we synthesized Cytos C and measured cell growth-inhibiting activities of 7 compounds, including Cytos A and C, in several human cancer cell lines. Among these compounds, Cytos C and tetradeoxycytosporolide A (TD-Cytos A), a model compound for the synthesis of Cytos A, had anti-proliferative effects on cancer cells, and TD-Cytos A exhibited stronger activity than Cytos C. In vitro topoisomerase-mediated DNA relaxing experiments showed that TD-Cytos A inhibited the activities of topoisomerase I and II, whereas Cytos C targeted only topoisomerase I. These data suggest that the anti-proliferative activities of Cytos correlate with the inhibition of topoisomerases and implicated TD-Cytos A as a novel anti-cancer drug that suppresses the activities of topoisomerase I and II.

C‑mannosylation of R‑spondin2 activates Wnt/β‑catenin signaling and migration activity in human tumor cells

R‑spondin2 (Rspo2), one of the four members of the R‑spondin family of proteins, has agonistic activity in the Wnt/β‑catenin signaling pathway, and it is associated with normal development, as well as disease, such as cancer. The present study focused on the C‑mannosylation of Rspo2, which is a novel and unique type of glycosylation that occurs via a C‑C linkage between the tryptophan residue and an α‑mannose. Although Rspo2 has two putative C‑mannosylation sites at residues Trp150 and Trp153, it had not been reported to date whether these sites are C‑mannosylated. Firstly, results from mass spectrometry demonstrated that Rspo2 was C‑mannosylated at the Trp150 and Trp153 residues. Notably, while this C‑mannosylation of Rspo2 resulted in increased extracellular secretion in human fibrosarcoma HT1080 cells, in other human tumor cell lines it inhibited secretion. However, C‑mannosylation had consistent effects on the activation of Wnt/β‑catenin signaling in PANC1 and MDA‑MB‑231 cells, as well as HT1080 cells. Furthermore, overexpression of wild‑type Rspo2 significantly increased the migratory ability of A549 and HT1080 cells, whereas overexpression of a C‑mannosylation‑defective mutant enhanced migration to a lesser degree. These results suggested that C‑mannosylation of Rspo2 may promote cancer progression and that the inhibition of C‑mannosylation may serve as a potential novel therapeutic approach for cancer therapy.

A novel computational approach for drug repurposing using systems biology

Motivation

Identification of novel therapeutic effects for existing US Food and Drug Administration (FDA)-approved drugs, drug repurposing, is an approach aimed to dramatically shorten the drug discovery process, which is costly, slow and risky. Several computational approaches use transcriptional data to find potential repurposing candidates. The main hypothesis of such approaches is that if gene expression signature of a particular drug is opposite to the gene expression signature of a disease, that drug may have a potential therapeutic effect on the disease. However, this may not be optimal since it fails to consider the different roles of genes and their dependencies at the system level.

Results

We propose a systems biology approach to discover novel therapeutic roles for established drugs that addresses some of the issues in the current approaches. To do so, we use publicly available drug and disease data to build a drug-disease network by considering all interactions between drug targets and disease-related genes in the context of all known signaling pathways. This network is integrated with gene-expression measurements to identify drugs with new desired therapeutic effects based on a system-level analysis method. We compare the proposed approach with the drug repurposing approach proposed by Sirota et al. on four human diseases: idiopathic pulmonary fibrosis, non-small cell lung cancer, prostate cancer and breast cancer. We evaluate the proposed approach based on its ability to re-discover drugs that are already FDA-approved for a given disease.

Availability and implementation

The R package DrugDiseaseNet is under review for publication in Bioconductor and is available at https://github.com/azampvd/DrugDiseaseNet.

Supplementary information

Supplementary data are available at Bioinformatics online.

Integrin β1 is an essential factor in vasculogenic mimicry of human cancer cells

Vasculogenic mimicry (VM) formation by cancer cells is known to play a crucial role in tumor progression, but its detailed mechanism is unclear. In the present study, we focused on integrin β1 (ITGB1) and assessed the role of ITGB1 in VM formation. We used in vitro methods to seed cancer cells on Matrigel to evaluate the capability of VM formation. We carried out ITGB1 gene deletion using the CRISPR/Cas9 system, and these ITGB1‐knockout cells did not show a VM‐like network formation. Further, reintroduction of ITGB1 rescued VM‐like network formation in ITGB1‐knockout cells. In conclusion, ITGB1 is a critical factor in VM of human cancer cells, and inhibition of ITGB1 may be a novel therapeutic approach for malignant cancer.

Enemies or weapons in hands: investigational anti-diabetic drug glibenclamide and cancer risk

Epidemiological evidence suggests that diabetes is associated with elevated cancer risk through the actions of hyperglycemia, hyperinsulinemia and chronic inflammation. Metformin, a first-line medication for type 2 diabetes mellitus, arouses growing concerns on its anti-cancer effect. However, data regarding the effect of glibenclamide on tumor growth and cancer risk are less consistent, which may be a potential anti-cancer drug. Areas covered: In this review, we clarified probable underlying mechanisms in preclinical studies and reviewed epidemiological evidence on glibenclamide's cancer risk in clinical studies. Glibenclamide inhibited carcinogenesis through ATP-binding cassette protein super-family and ATP-sensitive potassium channels, while majority of clinical researches reported an increased or non-significant elevated cancer risk of glibenclamide users compared with metformin users. Other sulfonylureas and diarylsulfonylureas were also briefly introduced. Expert opinion: The inconsistency between the results of studies was probably ascribed to undiscovered mechanisms, confounding factors, inconsistent comparators and publication bias. Existing clinical trials were prone to be afflicted by time-related bias including immortal time bias, time-window bias, and time-lag bias. Glibenclimiade could be a promising and well-tolerated anti-neoplastic drug targeting ATP-binding cassette protein super-family and KATP channels, but its efficacy still needs to be proven in well-designed long-term randomized controlled clinical trials.

N-glycosylation of R-spondin1 at Asn137 negatively regulates its secretion and Wnt/β-catenin signaling-enhancing activity

N-glycosylation is a post-translational protein modification with a wide variety of functions. It has been predicted that R-spondin1 (RSPO1) is N-glycosylated, although this remains unknown. The present study identified that RSPO1 was N-glycosylated at Asn137, and that N-glycosylation of RSPO1 negatively influenced its secretion and enhancing effect on Wnt/β-catenin signaling. In vitro treatment with peptide-N-glycosidase F increased the electrophoretic mobility of RSPO1. Furthermore, treatment of wild-type (wt) RSPO1-overexpressing HT1080 cells with tunicamycin (TM), which inhibits N-glycosylation, resulted in a significant reduction in the molecular weight of RSPO1. However, TM treatment had no effect in the RSPO1 mutant whereby the Asn137 residue was replaced by Gln (N137Q). These results demonstrated for the first time that RSPO1 is N-glycosylated at Asn137. RSPO1 is a secreted protein that has Wnt/β-catenin signaling-enhancing activity and is expected to have therapeutic applications. The role of N-glycosylation in RSPO1 was evaluated by conducting comparative experiments with wt and N137Q RSPO1, which revealed that the N137Q mutant increased the secretion and Wnt/β-catenin signaling-enhancing effect of RSPO1, compared with wt RSPO1. These results suggest that N-glycosylation of RSPO1 has a negative influence on its secretion and Wnt/β-catenin signaling-enhancing effect.

Identification of DPY19L3 as the C-mannosyltransferase of R-spondin1 in human cells

It was previously reported that human DPY19L3 is the C-mannosyltransferase of R-spondin1 at Trp-156. It is shown here that DPY19 family members have substrate specificity, providing insight into the function of C-mannosylation in cells.

R-spondin1 (Rspo1) is a secreted protein that enhances Wnt signaling, which has crucial functions in embryonic development and several cancers. C-mannosylation is a rare type of glycosylation and might regulate secretion, protein–protein interactions, and enzymatic activity. Although human Rspo1 contains 2 predicted C-mannosylation sites, C-mannosylation of Rspo1 has not been reported, nor have its functional effects on this protein. In this study, we demonstrate by mass spectrometry that Rspo1 is C-mannosylated at W¹⁵³ and W¹⁵⁶. Using Lec15.2 cells, which lack dolichol-phosphate-mannose synthesis activity, and mutant Rspo1-expressing cells that replace W¹⁵³ and W¹⁵⁶ by alanine residues, we observed that C-mannosylation of Rspo1 is required for its secretion. Further, the enhancement of canonical Wnt signaling by Rspo1 is regulated by C-mannosylation. Recently DPY19 was reported to be a C-mannosyltransferase in Caenorhabditis elegans, but no C-mannosyltransferases have been identified in any other organism. In gain- and loss-of-function experiments, human DPY19L3 selectively modified Rspo1 at W¹⁵⁶ but not W¹⁵³ based on mass spectrometry. Moreover, knockdown of DPY19L3 inhibited the secretion of Rspo1. In conclusion, we identified DPY19L3 as the C-mannosyltransferase of Rspo1 at W¹⁵⁶ and found that DPY19L3-mediated C-mannosylation of Rspo1 at W¹⁵⁶ is required for its secretion.

The Use of Glyburide Compared With Other Sulfonylureas and the Risk of Cancer in Patients With Type 2 Diabetes

OBJECTIVE

To determine whether the use of glyburide is associated with an increased risk of cancer compared with the use of other second-generation sulfonylureas among patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

The U.K. Clinical Practice Research Datalink was used to conduct a cohort study among 52,600 patients newly prescribed glyburide or other second-generation sulfonylureas between 1 January 1988 and 31 July 2013. A time-dependent Cox proportional hazards model was used to estimate adjusted hazard ratios (HRs) and 95% CIs of any cancer associated with the use of glyburide compared with the use of second-generation sulfonylureas. Secondary analyses were conducted to determine whether the association varied with cumulative duration of use and cumulative dose (expressed as defined daily dose [DDD]).

RESULTS

During 280,288 person-years of follow-up, 4,105 patients were given a new diagnosis of cancer (incidence rate 14.6 per 1,000 person-years). Overall, when compared with the use of other second-generation sulfonylureas, the use of glyburide was associated with a nonsignificant increased risk of any cancer (HR 1.09 [95% CI 0.98-1.22]). In secondary analyses, duration- and dose-response relationships were observed, with longer cumulative durations and cumulative doses associated with an increased risk of any cancer (>36 months: HR 1.21 [95% CI: 1.03-1.42]; >1,096 DDDs: HR 1.27 [95% CI 1.06-1.51]).

CONCLUSIONS

In this population-based cohort study, longer cumulative durations and higher cumulative doses of glyburide were associated with an increased risk of cancer.

Metformin reduces ovarian cancer risk in Taiwanese women with type 2 diabetes mellitus

BACKGROUND

Whether metformin therapy affects ovarian cancer risk in Asian patients with type 2 diabetes mellitus has not been investigated.

METHODS

Data analysis was performed in 2014. The reimbursement databases of Taiwanese female patients with a new diagnosis of type 2 diabetes mellitus between 1998 and 2002 (n = 479,475) were retrieved from the National Health Insurance for follow-up of ovarian cancer until the end of 2009. Metformin was treated as a time-dependent variable; and of these patients, 286,106 were never-users, and 193,369 were ever-users. A time-dependent approach was used to calculate ovarian cancer incidence and estimate hazard ratios by Cox regression for never-users (as referent group), ever-users and subgroups of metformin exposure (tertiles of cumulative duration and cumulative dose).

RESULTS

During follow-up, 601 metformin ever-users and 2600 never-users developed ovarian cancer, representing an incidence of 49.4 and 146.4 per 100,000 person-years, respectively. The overall fully adjusted hazard ratio (95% confidence intervals) for ever-users versus never-users was 0.658 (0.593-0.730). The fully adjusted hazard ratios for the first, second and third tertiles of cumulative duration of metformin therapy were 1.169 (1.019-1.341), 0.761 (0.644-0.898) and 0.276 (0.225-0.340), respectively (p trend < 0.01) and 1.220 (1.067-1.395), 0.610 (0.513-0.725) and 0.305 (0.248-0.374), respectively (p trend < 0.01), for a cumulative dose of metformin. In additional analyses, sulfonylureas but not the other antidiabetic drugs were associated with a reduced risk of ovarian cancer.

CONCLUSIONS

Metformin use is associated with a decreased risk of ovarian cancer.

Interference with distinct steps of sphingolipid synthesis and signaling attenuates proliferation of U87MG glioma cells

Glioblastoma is the most common malignant brain tumor, which, despite combined radio- and chemotherapy, recurs and is invariably fatal for affected patients. Members of the sphingolipid (SL) family are potent effectors of glioma cell proliferation. In particular sphingosine-1-phosphate (S1P) and the corresponding G protein-coupled S1P receptors transmit proliferative signals to glioma cells. To investigate the contribution to glioma cell proliferation we inhibited the first step of de novo SL synthesis in p53^wt and p53^mut glioma cells, and interfered with S1P signaling specifically in p53^wt U87MG cells. Subunit silencing (RNAi) or pharmacological antagonism (using myriocin) of serine palmitoyltransferase (SPT; catalyzing the first committed step of SL biosynthesis) reduced proliferation of p53^wt but not p53^mut GBM cells. In U87MG cells these observations were accompanied by decreased ceramide, sphingomyelin, and S1P content. Inhibition of SPT upregulated p53 and p21 expression and induced an increase in early and late apoptotic U87MG cells. Exogenously added S1P (complexed to physiological carriers) increased U87MG proliferation. In line, silencing of individual members of the S1P receptor family decreased U87MG proliferation. Silencing and pharmacological inhibition of the ATP-dependent cassette transporter A1 (ABCA1) that facilitates S1P efflux in astrocytes attenuated U87MG growth. Glyburide-mediated inhibition of ABCA1 resulted in intracellular accumulation of S1P raising the possibility that ABCA1 promotes S1P efflux in U87MG glioma cells thereby contributing to inside-out signaling. Our findings indicate that de novo SL synthesis, S1P receptor-mediated signaling, and ABCA1-mediated S1P efflux could provide pharmacological targets to interfere with glioma cell proliferation.

Assessment of in vivo and in vitro genotoxicity of glibenclamide in eukaryotic cells

Glibenclamide is an oral hypoglycemic drug commonly prescribed for the treatment of type 2 diabetes mellitus, whose anti-tumor activity has been recently described in several human cancer cells. The mutagenic potential of such an antidiabetic drug and its recombinogenic activity in eukaryotic cells were evaluated, the latter for the first time. The mutagenic potential of glibenclamide in therapeutically plasma (0.6 μM) and higher concentrations (10 μM, 100 μM, 240 μM and 480 μM) was assessed by the in vitro mammalian cell micronucleus test in human lymphocytes. Since the loss of heterozygosity arising from allelic recombination is an important biologically significant consequence of oxidative damage, the glibenclamide recombinogenic activity at 1 μM, 10 μM and 100 μM concentrations was evaluated by the in vivo homozygotization assay. Glibenclamide failed to alter the frequency of micronuclei between 0.6 μM and 480 μM concentrations and the cytokinesis block proliferation index between 0.6 μM and 240 μM concentrations. On the other hand, glibenclamide changed the cell-proliferation kinetics when used at 480 μM. In the homozygotization assay, the homozygotization indices for the analyzed markers were lower than 2.0 and demonstrated the lack of recombinogenic activity of glibenclamide. Data in the current study demonstrate that glibenclamide, in current experimental conditions, is devoid of significant genotoxic effects. This fact encourages further investigations on the use of this antidiabetic agent as a chemotherapeutic drug.

Activation of apoptosis by caspase-3-dependent specific RelB cleavage in anticancer agent-treated cancer cells: involvement of positive feedback mechanism

DTCM-glutarimide (DTCM-G) is a newly found anti-inflammatory agent. In the course of experiments with lymphoma cells, we found that DTCM-G induced specific RelB cleavage. Anticancer agent vinblastine also induced the specific RelB cleavage in human fibrosarcoma HT1080 cells. The site-directed mutagenesis analysis revealed that the Asp205 site in RelB was specifically cleaved possibly by caspase-3 in vinblastine-treated HT1080 cells. Moreover, the cells stably overexpressing RelB Asp205Ala were resistant to vinblastine-induced apoptosis. Thus, the specific Asp205 cleavage of RelB by caspase-3 would be involved in the apoptosis induction by anticancer agents, which would provide the positive feedback mechanism.

N-Glycosylation of extracellular matrix protein 1 (ECM1) regulates its secretion, which is unrelated to lipoid proteinosis

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Extracellular matrix protein 1 (ECM1) plays roles in extracellular matrix formation.

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Two ECM1 gene mutations observed in lipoid proteinosis patients suppress its secretion.

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ECM1 is N-glycosylated at Asn³⁵⁴ and Asn⁴⁴⁴ residues.

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N-linked glycan at Asn³⁵⁴ negatively regulated secretion of ECM1.

Extracellular matrix protein 1 (ECM1) is expressed in a wide variety of tissues and plays important roles in extracellular matrix formation. Additionally, ECM1 gene mutations cause lipoid proteinosis (LP), a rare skin condition of genetic origin. However, an effective therapeutic approach of LP is not established. Here, we showed that ECM1 gene mutation observed in LP patients significantly suppresses its secretion. As ECM1 has three putative N-glycosylation sites and most of mutated ECM1 observed in LP patients are defective in these N-glycosylation sites, we investigated the correlation between LP and N-glycosylation of ECM1. We identified that the Asn³⁵⁴ and Asn⁴⁴⁴ residues in ECM1 were N-glycosylated by mass spectrometry analysis. In addition, an N-linked glycan at Asn³⁵⁴ negatively regulated secretion of ECM1, contrary to LP patient-derived mutants. These results indicate that the defect of N-glycosylation in ECM1 is not involved in the aberration of secretion of LP-derived mutated ECM1.

Restoring TRAIL mediated signaling in ovarian cancer cells

Ovarian cancer has emerged as a multifaceted and genomically complex disease. Genetic/epigenetic mutations, suppression of tumor suppressors, overexpression of oncogenes, rewiring of intracellular signaling cascades and loss of apoptosis are some of the deeply studied mechanisms. In vitro and in vivo studies have highlighted different molecular mechanisms that regulate tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) mediated apoptosis in ovarian cancer. In this review, we bring to limelight, expansion in understanding systematical characterization of ovarian cancer cells has led to the rapid development of new drugs and treatments to target negative regulators of TRAIL mediated signaling pathway. Wide ranging synthetic and natural agents have been shown to stimulate mRNA and protein expression of death receptors. This review is compartmentalized into programmed cell death protein 4, platelet-derived growth factor signaling and miRNA control of TRAIL mediated signaling to ovarian cancer. Mapatumumab and PRO95780 have been tested for efficacy against ovarian cancer. Use of high-throughput screening assays will aid in dissecting the heterogeneity of this disease and increasing a long-term survival which might be achieved by translating rapidly accumulating information obtained from molecular and cellular studies to clinic researches.

N-glycosylation is required for secretion and enzymatic activity of human hyaluronidase1

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Hyaluronidase1 (HYAL1) is N-glycosylated at Asn⁹⁹, Asn²¹⁶, and Asn³⁵⁰.

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N-glycosylation regulates secretion of HYAL1.

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N-glycosylation is important for enzymatic activity of HYAL1.

Hyaluronidase1 (HYAL1) is a hydrolytic enzyme that degrades hyaluronic acid (HA) and has three predicted N-glycosylation sites at Asn⁹⁹, Asn²¹⁶, and Asn³⁵⁰. In this report, we show the functional significance of N-glycosylation on HYAL1 functions. Using mass spectrometry, we demonstrated that HYAL1 was N-glycosylated at the three asparagine residues. N-glycosylation of HYAL1 is important for secretion of HYAL1, as demonstrated by site-directed mutation. Moreover, a defect of N-glycosylation attenuated the enzymatic activity of HYAL1. Thus, HYAL1 is N-glycosylated at the three asparagine residues, and its secretion and enzymatic activity are regulated by N-glycosylation.

Identification of KvLQT1 K+ channels as new regulators of non-small cell lung cancer cell proliferation and migration

K+ channels, which are overexpressed in several cancers, have been identified as regulators of cell proliferation and migration, key processes in cancer development/propagation. Their role in lung cancer has not been studied extensively; but we showed previously that KvLQT1 channels are involved in cell migration, proliferation and repair of normal lung epithelial cells. We now investigated the role of these channels in lung cancer cell lines and their expression levels in human lung adenocarcinoma (AD) tissues. First, we observed that the wound-healing rates of A549 lung adenocarcinoma cell monolayers were reduced by clofilium and chromanol or after silencing with KvLQT1-specific siRNA. Dose-dependent decrease of A549 cell growth and cell accumulation in G0/G1 phase were seen after KvLQT1 inhibition. Clofilium also affected 2D and 3D migration of A549 cells. Similarly, H460 cell growth, migration and wound healing were diminished by this drug. Because K+ channel overexpression has been encountered in some cancers, we assessed KvLQT1 expression levels in tumor tissues from patients with lung AD. KvLQT1 protein expression in tumor samples was increased by 1.5- to 7-fold, compared to paired non-neoplastic tissues, in 17 of 26 patients. In summary, our data reveal that KvLQT1 channel blockade efficiently reduces A549 and H460 cell proliferation and migration. Moreover, KvLQT1 overexpression in AD samples suggests that it could be a potential therapeutic target in lung cancer.

Effects of sulfonylureas on tumor growth: a review of the literature

Type 2 diabetes mellitus patients are at higher cancer risk, probably because of hyperinsulinemia and insulin growth factor 1 pathway activation. The effects of antidiabetic drugs on cancer risk have been described and discussed in several studies suggesting opposite effects of the biguanide metformin and sulfonylureas on cancer incidence and mortality. The anticancer mechanisms of metformin have been clarified, and some clinical studies, particularly in breast cancer patients, have been published or are currently ongoing; however, data about the effects of sulfonylureas on cancer growth are less consistent. The aims of this work are to review preclinical evidence of second-generation sulfonylureas effects on tumor growth, to clarify the potential mechanisms of action, and to identify possible metabolic targets for patient selection. Most evidence is on the adenosine triphosphate-sensitive potassium channels inhibitor glibenclamide, which interacts with reactive oxygen species production thus inducing cancer cell death. Among diarylsulfonylureas, next-generation DW2282 derivatives are particularly promising because of the proapoptotic activity in multidrug-resistant cells.